196 



Conservation Department 



Relation of Bottom to Quantity of Food. — Table 2 shows 

 the stream bottom types studied and the relative amounts of food 

 found on each type of bottom. Silt bottom supported the greatest 

 amount of fish food, there being an average of 4.29 grams in one 

 square foot. Bubble sheltered the next largest amount in having 

 1.88 grams per square foot. Coarse gravel was nearly as productive 

 as rubble, having 1.281 grams. Fine gravel, muck and sand offered 

 about the same amounts, while hardpan and bedrock were very 

 poor in food. Chart 1 shows graphically the relative amounts found 

 on the different types of bottom. 



Comparison of Quantity of Food in Stream and Pool Bot= 

 toms. — Unit area bottom studies were made in pools to determine 

 the forage possibilities which pool bottoms offer as compared with 

 stream bottoms. The average amount of available fish food by 



Table 2. — Showing Stream Bottom Types of Available Fish Food 



NUMBER SQUARE FEET TAKEN 



Type of bottom 



Average 



weight 



in grams 



per sq. ft. 



4 



Silt 



4.29 



12 



Rubble 



Coarse gravel 



1.88 



18 



1.281 



7 



Fine gravel 



Muck 



.98 



1 



.65 



2 



Sand 



.46 



1 



Hardpan 



.1 



1 



Bedrock 



.0065 









Average for all sq. ft 1.21 grams 



weight in one square foot of pool bottom was found to be .26 

 grams, covering all types and sizes of pools. The average amount 

 of available food by weight in one square foot of stream bottom 

 was 1.21 grams covering all types of streams. By dividing it it is 

 seen that the food, by weight, in one square foot of stream bottom 

 is approximately 4.6 times as rich as the same size area in a pool 

 bottom, i.e., there is 4.6 times the potential food in a stream bottom 

 as compared to pool bottoms. The pool bottoms and stream 

 bottoms in which these studies were made contained little or no 

 aquatic vegetation which, when abundant, supports large numbers 

 of animals. The populations of submerged plant beds are con- 

 sidered in another section of this report. 



The low average weight of food found in a unit area of pool 

 bottom is somewhat compensated for by the fact that there is 

 greater area for foraging in a pool per given unit of stream, because 

 pools are generally wider and deeper than the average for the 

 stream. 



